Drum refiners of the general type discussed above are known to the prior art, U.S. Pat. No. 4,275,852 describes the general operation of such drum refiners. Unrefined pulp material introduced into a cylindrical drum is propelled therethrough in rapid pulsating succession while being subjected to a wedging action as it is accelerated by the centrifugal force exerted by the wings. Rotating wings exert a force in a linear/radial direction on the material, causing it to become compacted into wedge-shaped clumps, As explained more fully in the afore-mentioned U.S. Pat. No. 4,275,852, a plane of shear created a short distance from the leading edge of the wings breaks up the fiber bundles, and the refining action takes place when shearing forces are induced between the rotating clumps of pulp which are held back by friction generated against the interior drum surface. However, a separate blade element is mounted along one surface of each wing, and the edge of the blade closest to the drum surface may be deflected relative to the fixed wing. Deflection of this leading edge of the blade results in angular adjustment of the blade relative to the inner surface of the drum.
U.S. Pat. No. 3,547,356 discloses a drum refiner in which rotatable blades are designed to remain at a fixed distance during the refining action. The gap between the blades and the inner surface of the cylindrical drum is adJusted in part by adjustable cams mounted on the inner surface of the cylindrical drum.
U.S. Pat. No. 4,199,114 also discloses a drum refiner in which the gap between a rotatable impeller and a series of shear members in the inner surface of the cylindrical drum is regulated by staves adjustably mounted to the inner surface of the drum, the linear movement of the pulp material through the drum being controlled by a series of plow members.
U.S. Pat. Nos. 1,951,519, 2,216,612 and 3,806,050 provide further illustrations of known drum refiners. In U.S. Pat. No. 1,951,519, a bed plate fitted with a plurality of bars or knives is adjustably mounted to the inner surface of the drum so as to selectively adjust the gap between the inner surface of the drum and a rotor having a plurality of knives.
U.S. Pat. No. 2,216,612 discloses a drum refiner including a rotor having fixed arms. Knives mounted to the end of the arms are slidably adjustable relative to the inner surface of the drum by removing a locking bolt and then by turning an adjustment bolt.
U.S. Pat. No. 3,806,050 discloses a drum refiner in which interchangeable blocks having a plurality of teeth are arranged in desired patterns to accomplish optimum mixing and refining.
It is among the objects of the present invention to provide an improved mixing/refining system in which the drum refiner includes means for repeated high frequency compression of the pulp material in a radial direction as well as in a linear direction.